Gas flow sensor and high pressure gaseous fuel injection system

Abstract

A novel flow sensor that includes a valve responsive to a pressure differential or pressure drop across a selectively sized restriction orifice. The flow sensor may be incorporated into a high-pressure fuel injection system for sensing the opening and closing of high pressure fuel injector for injecting gaseous fuel.

What is claimed is:  
     
       1. A gas flow sensor for sensing flow, comprising: 
       a flow sensor body assembly having an internal chamber, an inlet passage and an outlet passage;  
       a piston linearly reciprocable in the internal chamber;  
       a position sensor axially aligned with the piston and in sensory communication with the piston, having an output indicating the position of the piston relative to the flow sensor body assembly, the position sensor providing only an on-off output rather than a variable output;  
       a fixed size restriction orifice between the inlet passage and outlet passage dividing the internal chamber into an inlet pressure region acting on a first end portion of the piston and an outlet pressure region acting on a second end portion of the piston, the restriction orifice being sized to create a pressure differential across the piston when gas flows through at least one of the inlet and outlet passages; and  
       wherein the piston is biased to one position, said pressure differential is adapted to overpower the force of the bias to move the piston toward a second position.  
     
     
       2. The gas flow sensor of  claim 1  wherein the flow sensor body assembly includes a body and a sleeve mounted in the body, the piston being mounted for sliding movement in a cylindrical bore defined by the sleeve the cylindrical bore including spaced apart first and second guide portions engaging the surface of the piston and an annular gap between the piston and the sleeve at a location between the first and second guide portions, the annular gap providing the restriction orifice, said annular gap connecting the inlet pressure region and the outlet pressure region. 
     
     
       3. The gas flow sensor of  claim 2  wherein the body and piston are made of non-magnetic material, the piston having a magnetic target mounted in one end of the piston, and wherein the sensor is a hail effect detector mounted in the body proximate said one end of the piston but completely fluidically isolated from the chamber by a partition of non-magnetic material integrally in the body for safety purposes when the gas is a fuel, the hall effect detector adapted to sense a change in magnetic field based on the position of the target mounted in the piston. 
     
     
       4. The gas flow sensor of  claim 3  wherein the piston is plastic, the body is aluminum and the sleeve is steel. 
     
     
       5. The gas flow sensor of  claim 3  wherein the hall effect detector is mounted in a sensor chamber defined in the body, the flow sensor body assembly further comprising a cover plate enclosing the sensor chamber. 
     
     
       6. The gas flow sensor of  claim 3  further comprising a spring providing said bias mounted in a spring cavity defined partly by one end of the piston and a retaining plug securing the piston guide sleeve inside the valve body, the spring engaging the retaining plug, further including at least one relief hole formed in the piston connecting the spring chamber with the outlet pressure region. 
     
     
       7. A gas flow sensor, for interposition between a high pressure source of gas and a valve having an outlet orifice for discharging the gas comprising: 
       a body having an internal chamber, an inlet passage for connection to the high pressure source and an outlet passage for connection to the valve;  
       a guide sleeve mounted in the body defining a cylindrical bore;  
       a retaining plug securing the guide sleeve in the body;  
       a piston mounted in the cylindrical bore for linear sliding movement therein, the guide sleeve providing spaced apart first and second guide portions engaging the surface of the piston;  
       a position sensor in sensory communication with the piston, having an electrical output indicating the position of the piston relative to the body;  
       a restriction orifice arranged between the inlet passage and the outlet passage dividing the internal chamber into a inlet pressure region acting on a first end portion of the piston and an outlet pressure region acting on a second end portion of the piston, wherein a pressure drop is effected across the restriction orifice when gas flows out the outlet passage, wherein the restriction orifice is an annular gap defined between the piston and sleeve at a location between the first and second guide portions, said annular gap connecting the inlet and outlet passages; and  
       a spring biasing the piston to one position, said pressure drop adapted to overpower the force of the spring to move the piston toward a second position.  
     
     
       8. The gas flow sensor of  claim 7  wherein the body and piston are made of non-magnetic material, the piston having a magnetic target mounted in one end of the piston, and wherein sensor is a hall effect detector mounted in the body proximate said one end of the valve piston but completely fluidically isolated from the chamber by a partition of non-magnetic material integrally in the body for safety purposes when the gas is a fuel, the hall effect detector adapted to sense a change in magnetic field based on the position of the target mounted in the piston. 
     
     
       9. The gas flow sensor of  claim 8  wherein the piston is plastic, the body is aluminum and the sleeve is steel. 
     
     
       10. The gas flow sensor of  claim 9  wherein the hall effect detector is mounted in a sensor chamber defined in the body, the flow sensor body assembly further comprising a cover plate enclosing the sensor chamber. 
     
     
       11. The gas flow sensor of  claim 8  wherein the body is formed from a solid block to include a first cavity at one end of the solid block in which the guide sleeve and piston are slidably inserted such that they are capable of being slidably removed for maintenance, the retaining plug being screwed into the valve body to enclose the first cavity and being removable to allow for maintenance, the retaining plug supporting the spring. 
     
     
       12. The gas flow sensor of  claim 11  wherein the body includes a second cavity at another end of the solid block, the position sensor mounted in the second cavity. 
     
     
       13. The gas flow sensor of  claim 12  wherein the first cavity includes an annular shoulder between the inlet passage and outlet passage supporting the sleeve against an axial retaining force of the retaining plug. 
     
     
       14. The gas flow sensor of  claim 7  wherein the position sensor is axially aligned with the piston, and wherein the position sensor provides only an on-off output rather than a variable output.